Yarn keeps all project files ignoring what is defined on package.json's "files" prop

[melloc01]

Do you want to request a feature or report a bug?
Report a bug.

What is the current behavior?
yarn keeps all the project files when using a git project as dependency. npm keeps only the files on the "files" config prop.

If the current behavior is a bug, please provide the steps to reproduce.
1 - Use this repo as dependency of a project.
2 - Install via yarn
3 - Install via npm

contents on node_modules will differ.

What is the expected behavior?
As descripted on the docs

""files" field is an array of file patterns that describes the entries to be included when your package is installed as a dependency."

So it is expected to only have the files listed on the config to be present.

Please mention your node.js, yarn and operating system version.

• Deepin Linux@15.5
• yarn@1.3.2
• npm@5.6.0

[rally25rs]

duplicate #2822